1. Field of the Invention
This invention relates to a one-way clutch (cam clutch) for use as a part for torque transmission, back stop or the like, for example, in the driving apparatus of an automobile (particularly an automatic transmission for an automobile), a two-wheeled vehicle, an industrial machine or the like, and more particularly to an improvement in a construction for giving a drag torque to between a holder and an outer race.
2. Related Background Art
Generally, a sprag type one-way clutch 100 (the double cage type) provided with a sprag functioning as a cam, as shown in FIG. 10 of the accompanying drawings, comprises an outer race 110, an inner race 120 disposed for rotation relative to the outer race 110, an annular inner holder 135 and an outer holder 136 disposed between the outer race 110 and the inner race 120, a plurality of sprags 130 equidistantly held by the inner and outer holders 135 and 136, a ribbon spring member 138 for biasing the sprags 130 in a meshing direction, and end bearings 132 disposed at the axially opposite ends to maintain the concentricity of the outer race 110 and the inner race 120.
The end bearings 132 of the one-way clutch 100 are axially held by an annular snap ring 131 and an annular retainer 134 fixed to the outer race to prevent them from axially coming off. The sprags are given a rising moment in a direction to mesh with the raceway surfaces of the inner and outer races by the ribbon spring member 138.
Generally, in the one-way clutch, when there is sudden acceleration or deceleration in the rotation of the outer race, the sprags slide on the raceway surfaces of the outer race due to inertia and the timing of meshing is delayed and therefore, a frictional force (drag torque) is sometimes given to between the outer holder and the outer race to thereby rotate them always as a unit. This is for quickly transmitting the movement of the outer race to the outer holder and securing the movement of the sprags. Therefore, a cut-away is formed in the circumferential surface of the outer holder, that is, T-bar working or i-bar working is effected, and this is deformed and forced into the outer race, or instead of the cut-away, a drag clip or the like is mounted on the outer holder to thereby obtain a predetermined frictional force. See, for example, Japanese Laid-Open Patent Application No. 1-188726.
For example, in FIG. 10, an i-bar 137 is formed on a portion of the outer holder 136 in the circumferential direction thereof to frictionally slide on the inner raceway surface of the outer race 110 and give a frictional force. Since predetermined drag torque is provided by this i-bar 137, the outer race 110 and the outer holder 136 always rotate as a unit.
Also, in a one-way clutch (the single cage type) wherein only one holder is provided between the inner and outer races, a cut-away was formed in a side plate as a member for giving a frictional force to between it and one of the inner and outer races. See, for example, U.S. Pat. No. 5,038,903.
However, the cut-away formed in the circumferential direction of the outer holder has led to a problem in the strength of the holder and a problem in terms of working. Also, in a one-way clutch (the single cage type) in which only one holder is provided between the inner and outer races, it has been difficult to give a drag as in the prior art when a side plate is not used.